Hydrocephalus is a neurological condition caused by the abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles, or cavities, of the brain. Hydrocephalus, which can affect infants, children and adults, arises when the normal drainage of CSF in the brain is blocked in some way. Such blockage can be caused by a number of factors, including, for example, genetic predisposition, intraventricular or intracranial hemorrhage, infections such as meningitis, or head trauma. Blockage of the flow of CSF consequently creates an imbalance between the rate at which CSF is produced by the ventricular system and the rate at which CSF is absorbed into the bloodstream. This imbalance increases pressure on the brain and causes the ventricles to enlarge. Left untreated, hydrocephalus can result in serious medical conditions, including subdural hematoma, compression of the brain tissue, and impaired blood flow.
Hydrocephalus is most often treated by surgically inserting a shunt system to divert the flow of CSF from the ventricle to another area of the body, such as the right atrium, the peritoneum, or other locations in the body where CSF can be absorbed as part of the circulatory system. Various shunt systems have been developed for the treatment of hydrocephalus. Typically, shunt systems include a ventricular catheter that extends into the ventricle of a patient, a shunt valve for controlling the flow rate of fluid draining from the ventricle, and a drainage catheter extending from the shunt valve into another area of the body. Typically, the shunt valve is palpatable by the physician through the patient's skin after implantation.
It is important to be able to externally read or verify the setting of the valve in conjunction with adjusting its characteristics. With some adjustable valves, x-ray images are used to determine the current setting of the valve, before and after adjustment. With other adjustable valves, the orientation of a rotor in the valve can be read magnetically, using a magnetic compass-like device positioned above the valve, outside the skin of the patient. Such a device is known as an indicator tool. Some valve adjustment systems utilize a separate adjuster tool for adjusting the characteristics of the valve. Both the adjuster tool and the indicator tool can be used in conjunction with a locator tool. The locator tool is designed to be placed over the valve site to indicate the location and orientation of the valve under the skin, and subsequently to maintain the locator tool in position relative to the established position and orientation of the valve. When the position has been established, the adjuster and indicator tools can be engaged within the locator tool to perform their respective functions.
Although tools and methods exist for adjusting CSF shunt valve settings, as do other tools and methods for reading a valve setting, some have difficulty performing their function if the underlying valve protrudes too far from the skull into the locator tool. This may happen due to swelling or in instances where the patient has a thick or thin scalp, or a smaller or larger skull than is typical. In these instances, the valve can interfere with the placement and operation of the adjustor and/or indicator tools. Parallel placement of the locator to the implanted valve whilst in closest proximity to the implanted valve whilst permitting complete engagement between the locator and the indicator and adjustment tools enables successful operation of these tools.
Accordingly, a need exists for tools that enable the locator to be held by the user against the skin in a position generally parallel to the implanted valve, while preventing interference between the skin/valve and the adjustor and indicator tools.